Conventional pulse oximetry has significant limitations because it works on the assumption that there are only two species of hemoglobin present: oxygenated hemoglobin (O2Hb) and reduced hemoglobin (RHb). In reality, two other hemoglobin species -- carboxyhemoglobin (COHb) and methemoglobin (metHb), collectively termed dyshemoglobins -- are present at all times. These two species of hemoglobin are formed endogenously at very low levels, but their quantities can increase to dangerous levels when carbon monoxide is present in inspired air or as a reaction to certain drugs or chemicals in the environment. All pulse oximeters used in medicine today, representing over 1,000,000 units worldwide, read oxygenation levels that are too high when there are elevated levels of dyshemoglobins in the blood. The alternative to pulse oximetry is to analyze arterial blood with a laboratory CO-oximeter. This procedure involves several different health care workers, potentially exposes personnel to blood borne pathogens, takes minutes or even hours to get results, and provides only a single data point in time. All of this adds cost, increases risks to health care workers, and delays appropriate treatment. Previous attempts by various companies to develop a noninvasive method of CO-oximetry have not succeeded. The limiting factors have been the correct selection of optical emitter wavelengths, spectral bandwith of the emitters, and troublesome power instabilities of the requisite laser light sources. Kestrel Labs has recently developed a new Optical Stabilization Method that will make possible the use of laser light for accurate photoplethysmographic measurements, and thus make possible the world's first, commercially-viable, noninvasive CO-oximeter. This new type of medical monitor, termed a Pulse CO-Oximeter, will provide clinicians with a powerful, cost saving new tool for patient diagnosis and care. This SBIR Phase I effort focuses on computer simulations and empirical validation of this new Optical Stabilization Method [unreadable] [unreadable]